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This paper investigates the nonlinear relationship between capital structure and firm performance in the MENA region using a sample of 499 listed firms over the 2007–2020 period, or 6986 firm-year observations. Specifically, we examine the size-threshold effect in the capital structure–firm performance nexus. To do so, this study applies a dynamic panel threshold regression model (DPTR). The findings show that there is a nonlinear relationship between debt and firm performance (Tobin’s Q, ROA, and ROE). Specifically, the threshold values of firm size for the three models are estimated at 9.126 (about $1 million), 15.48 (about $5 million), and 16.816 (about $20 million), respectively, between the low- and the high-sized regimes. In the lower regime, the firm’s value (Q) increases when debt increases; however, in the higher regime, this value decreases when debt increases. Furthermore, in the lower regime, the performances (ROA and ROE) of small firms decrease when debt increases; however, in the upper regime, when debt increases, the performances of large firms increase. The results are several robustness tests. These results support the predictions of signal, pecking order, and trade-off theories. Managers of large (small) MENA firms should increase (decrease) the use of debt to improve performance.

This work was performed to dig into the phytochemical composition and bioactivities of Nocardiopsis sp. UR67 associated with the marine sponge Callyspongia sp. It was fermented in suspension and immobilised in calcium alginate bead cultures. The ethyl acetate extracts, afforded from the broth in each case named EG-49 and J-48g, respectively, revealed 16 chemical principles mostly belonging to polyketides, macrolides, and peptides. EG-49 and J-48g displayed anti-Candida albicans activity with IC50 values of 8.1 and 8.3 µg/mL, and a substantial cytotoxic effect against lung adenocarcinoma H1650 at IC50 12.6 and 13.7 µg/mL, respectively. However, only EG-49 exhibited a noteworthy anti-trypanosomal activity at 7.5 µg/mL. Molecular docking of the characterised compounds against Trypanosoma brucei trypanothione reductase demonstrated the highest binding models of griseochelin-methyl ester (9) and filipin-II (11), which drew considerable significance of the metabolites derived from Nocardiopsis sp. UR67 developing potential T. brucei trypanothione reductase inhibitors.

Brassica juncea (B. juncea) is an erect, often unbranched plant belongs to family Brassicaceae. Its seeds have been used in many countries to treat considerable common and chronic diseases as a folk remedy. The current study designed to investigate the in vitro and in vivo anticandidal effect of hydroehanolic extract of B. juncea seeds. Besides determine its bioactive compounds using gas chromatography–mass spectrometry (GC–MS) analysis. Regarding, in vitro experiment, isolated Candida pelliculosa from blood and urine were used for the assessment of the antimicrobial effects of the extract. Considering in vivo study hepatoprotective effect of B. juncea extract against candidal-induced infection was estimated in male and female rats. The animals divided into four groups for each sex. Control group, B. juncea extract treated group, Candida infected group and infected group treated with B. juncea. Animals treated with tested extract 72 h post infection once daily for 14 days. Liver function test, liver glutathione (GSH) and lipid peroxidation (LPO) content were estimated as well as investigation of histological sections of liver. the extract displayed significant in vitro and in vivo anticandidal effect through alleviating its induced hepatotoxicity caused by infection either by significant decreased of liver enzymes and LPO or enhancing hepatic GSH content. Histopathological examination of the respective organs confirmed these findings. The GC–MS analysis of the extract revealed the presence of 17 components; Eremanthin considered as the main component (55%) considered as a potent antioxidant; may contribute to its hepatoprotective activity. These results indicated that the hydroehanolic extract of B. juncea seeds exhibits inhibitory effect against hepatotoxicity caused by candidiasis.

The chemical profiling of the main phytoconstituents of total ethanolic extract (TEE) and its different fractions of Bignonia binata leaves was dereplicated using liquid chromatography–high resolution-electrospray ionisation–mass spectrometry (LC-HR-ESI-MS), revealed the presence of various classes of secondary metabolites; eight phenylethanoids, two flavonoidal glycosides and two iridoids. Moreover, the hepatoprotective and nephroprotective activities of the TEE and its different fractions were investigated in carbon tetrachloride (CCl4)-intoxicated rats and were compared with those of silymarin-treated group, revealing the highest potency of the EtOAc group, followed by the aqueous one in improving the CCl4-induced alterations in several biochemical parameters. Besides, EtOAc and aqueous fractions exhibited the most inhibition of CCl4-induced inflammatory mediators and improving the changes in the histopathological structures of the liver and kidney. In addition, the EtOAc fraction demonstrated the highest total phenolic content, whereas TEE showed the highest amount of total flavonoid content.

Anti-inflammatory effects of the total ethanol extract and the different fractions of C. myxa L. leaves using carrageenan â induced paw edema method. (DOCX 94 kb)

DPPH radical scavenging activity of the total ethanol extract and the different fractions of C. myxa L. leaves. (DOCX 150 kb)

Antioxidant capacities of the total ethanol extract and the different fractions of C. myxa L. leaves using phosphomolybdate assay. (DOCX 22 kb)

Total flavonoid content of the total ethanol extract and the different fractions of C. myxa L. leaves. (DOCX 27 kb)

Additional file 1. Additional figures.

Antipyretic effects of the total ethanol extract and the different fractions of C. myxa L. leaves using Yeastâ induced pyrexia method. (DOCX 94 kb)

Antidiabetic effects of the total ethanol extract and the different fractions of C. myxa L. leaves using streptozotocin-induced hyperglycemia method. (DOCX 96 kb)

Total phenolic content of the total ethanol extract and the different fractions of C. myxa L. leaves. (DOCX 26 kb)

Both ethyl acetate and aqueous fractions of Tabebuia aurea leaves exhibited noteworthy antioxidant and nephroprotective activities against carbon tetrachloride (CCl4)-induced nephrotoxicity in rats, as evidenced by the remarkable improvements of renal serum biomarkers and histopathological features. Additionally, the ethyl acetate fraction displayed a prominent in vitro antitrypanosomal activity against Trypanosoma brucei; consequently, the leaves were subjected to LC-HR-ESI-MS metabolomic profiling to discover the constituents that possibly underlie their bioactivities. Therefore, ten metabolites were characterized, mostly dominated by flavonoids. Interestingly, two identified constituents viz., 3,9,12,15-octadecatetraenoic acid (9) and 9,11,13-octadecatrienoic acid (10) are reported firstly herein from the genus Tabebuia. Furthermore, among the dereplicated constituents, rutin (5) and kaempferol 3-O-rutinoside (6) exhibited the highest docking scores as effective antitrypanosomal compounds.

Analgesic effects of the total ethanol extract and the different fractions of C. myxa L. leaves using hot plate method. (DOCX 93 kb)